Gas streams produced from subsurface reservoirs such as natural gas, associated gas and coal bed methane or from (partial)oxidation processes, usually contain in addition to the gaseous product concerned such as methane, hydrogen and/or nitrogen gaseous contaminants such as carbon dioxide, hydrogen sulphide, carbon oxysulphide, mercaptans, sulphides and aromatic sulphur containing compounds in varying amounts. For most of the applications of these gas streams, the contaminants need to be removed, either partly or almost completely, depending on the specific contaminant and/or the use. Often, the sulphur compounds need to be removed into the ppm level, carbon dioxide sometimes into the ppm level, e.g. LNG applications, or down to 2 or 3 vol. percent, e.g. for use as heating gas. Higher hydrocarbons may be present, which, depending on the use, may be recovered.
A way to remove such gaseous contaminants is to liquefy them and to remove the liquid so obtained by means of a liquid/gas separation method.
In WO 2008/082291 A1 and WO 2005/118110 A1, separation devices have been described for removing liquefied contaminants, such as carbon dioxide and hydrogen sulphide, from a natural gas stream. Said separation devices comprise a normally horizontal centrifugal separator to establish the separation of the liquefied contaminants from the gas stream to obtain a contaminants-enriched liquid phase and a contaminants-depleted gaseous phase.
A disadvantage of these known separation devices is, however, that there is still considerable room for improving the efficiency of removing the liquefied contaminants from the feed stream, ensuring that levels can be reached that are close to the thermodynamic prediction for the degree of condensation of the contaminants. Also, there is room for improvement of the liquid handling system, ensuring a more compact, lighter weight, minimal footprint, separation device.